Igniting aid for high efficiency plasma producers

ABSTRACT

An ignition device for high efficiency plasma producers, which device precludes the necessity for extremely high voltages to produce the initial ignition of the plasma producer by providing high specific ionic densities between the electrodes thereof. The ignition device consists of an annular passage surrounding a rod electrode and through which ionizable gas is passed. The cylindrical wall which defines the outer periphery of the annulus continues axially beyond the end of the rod electrode to form a first tubular passage. A further cylindrical wall forms a second larger diametered tubular passage beyond said first tubular passage. An arc is struck between the rod electrode and the cylindrical wall forming the second tubular passage, which arc has electric lines of force in the form of a cone with the apex pointing upstream the direction of the flow of the ionizable gas. The cone-shaped arc has an azimuthal magnetic field on the inside and outside thereof, and as the gas goes through the arc it is partially ionized and the opposite charge carriers are radially separated by the azimuthal magnetic field. By virtue of the separation, there is less tendency for the opposite charge carriers to recombine, and consequently there is a higher specific ionic density when the gas is introduced between the electrodes of the high efficiency plasma producer.

l 9 l 2 l o O5-l8-7l XR 3,579,027

[72] Inventor Maximilian Pater Primary ExaminerRaymond F. HossfeldVienna, Austria A uorney Glascock, Downing &- Seebold [2|] Appl. No.710,175

[22] Filed Mar. 4, 1968 [45] Patented May 18, 1971 ABSTRACT: An ignitiondevice for high efficiency plasma [73] Assignee Gebr. Bohler & Co.Aktiengesellsclum producers, which device precludes the necessity forextremely Vienna, Austria high voltages to produce the initial ignitionof the plasma [32] Priority Mar. 3, 1967 producer by providing highspecific ionic densities between [33] Ami. the electrodes thereof. Theignition device consists of an an- [3l] A203l/67 nular passagesurrounding a rod electrode and through which ionizable gas is passed.The cylindrical wall which defines the outer periphery of the annuluscontinues axially beyond the 54) IGNIIING AID FOR nlcu EFFICIENCY PLASMAa first Passage- A PRODUCERS further cylmdncal wall forms a secondlarger dlametered tubular passage beyond said first tubular passage. Anare is 7 Claims, 1 Drawing Fig.

struck between the rod electrode and the cylindrical wall forming thesecond tubular passage, which are has electric 2 1. e lines of force inthe form of a cone with the apex pointing up- [5 i IIZIL Cl H01] streamthe direction of the flgw of the ionizable gas. The cone- [50] 313/197,shaped age has an azimuthal magnetic field on the inside and h 315/! l219/121 outside thereof, and as the gas goes through the arc it ispartially ionized and the opposite charge carriers are radially [56]Refcnm CM separated by the azimuthal magnetic field. By virtue of theUNITED STATES PATENTS separation, there is less tendency for theopposite charge car- 2,508,954 5/1950 Latour et al. 313/231X riers torecombine, and consequently there is a higher specific 3,370,198 2/1968Rogers et al. 3 15/ l l l ionic-density when the gas is introducedbetween the elec- 3,425,223 2/ i969 Browning 60/203 trodes of the highefficiency plasma producer.

III] Patented May 18, 1971 I 3,579,027

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Br ML 7 "M IGNKTKNG All) FOR HIGH EFFICIENCY PLASMA PRODUCERS Apparatusfor the production of plasma operates, in general, with the help of anelectric arc through which the gas to be converted into plasma isdirected, and by which it is ionized. High efficiency apparatus of largesize have at least one complication in that there is too great adistance between the electrodes, and the initial ignition of the plasmaproducing arc can be accomplished only with the greatest of difficulty.

A way for overcoming this difficulty consists, for example, in theproduction of a short duration high induction voltage between theelectrodes, but this measure carries the disadvantage of the greatnumber of coil windings necessary for this purpose. l-ligh resistanceoccurs in the part of the apparatus providing the current. Anotherpossibility, difficult to place in practice, could consist of a primaryarc to be ignited between a cathode and an auxiliary graphite electrode,which are is transmitted to a second electrode, and then the auxiliaryelectrode can be removed.

An electric arc ignition apparatus is already known in which separateignition electrodes have been utilized and through which, for example, acondenser is discharged. The quasineutral plasma which has been producedfrom this discharge is directed between the electrodes of the electricarc and serves for the preliminary ionization, whereby naturally aconsiderable part of the positive and negative ions produced is lost, inproportion to the distance to betravelled, on account of recombinationof the opposite charge carriers.

If however, in accordance with the instant invention, the gas to beionized is directed through an are having the shape of a cone, or in theextreme case through an approximately discshaped arc, an azimuthalmagnetic field is produced, leading to a separation of different chargecarriers in the plasma, and also after a dissipation of the electronsthere is an excess of positive charge carriers. On account of thisdissipation of their negative counterparts over long distances, thepositive charge carriers have no opportunity to neutralize, so that incomparison with the already known procedures, there results theadvantage of maintaining for a longer period the ionized state of theauxiliary gas stream.

A further advantage of this invention in comparison with the alreadyknown procedures, consists in the possibility of operating withconsiderably lower voltage for ionization.

The method according to the invention consists therefore in the factthat the medium to be ionized is directed through a conical arc, and inthe extreme case, a disc-shaped are when viewed along the electrode. Theions produced therein are led into the space between the electrodes ofthe high efficiency plasma producer to be ignited, so that the voltagenecessary to produce the initial ignition is greatly lowered on accountof the relatively high specific ionic densities. This method may becarried out by an apparatus which contains essentially the elements ofan ordinary electric ignition sparkplug, namely, a central electrodepreferably in rod form; an isolating body surrounding it at leastpartially; a counterelectrode which is shaped so that between it and therod-shaped electrode there burns a conic or in the borderline case adisc-shaped arc; as well as additionally a stopping or securing device,a gas feeder, and a gas channel going through the sparking area. Thesetypes of plasma sparking plugs can be screwed into any plasma producerand changed in a simple way and manner at any time. The necessaryauxiliary sparking voltage can be realized with less effort due to thesmaller requirements for the operation of the plasma spark plug. Therequired electric current produced by passing a gas medium to be ionizedthrough an arc-shaped cone and in the extreme case a disc, andthereafter the gas medium in at least a partially ionized state isbrought into the space between the electrodes of the high efficiencyplasma producer.

Both electrodes, between which the conical arc burns, do not necessarilyhave to be part of the plasma ignition spark plug. In the preferredform, the plasma producer in which the plasma ignition spark plug isfixed, serves as a counterelectrode. If the ignition spark plugelectrode has been shaped as a rod electrode, as in the case with theusual electric spark plug, it is advantageous to make the isolating bodywhich is surrounding it long enough to over reach the electrode tip inorder to prevent a backfiring of the spark.

Referring now to the drawing, it will be seen that the ignition aidcomprises a rod electrode 1 which is connected to a current source andis contained in an isolating cylindrical body 2. An annular securingmeans 3 for the ignition aid is screwed into a plasma producer 5, andpreferably the plasma producer acts as a counterelectrode and is alsoconnected to the current source. The gas to be ionized is introducedthrough a coupling 6, down through a gas feeding annular channel 4 andthrough a conical are 7 which is struck between the end of rod electrode1 and the inner cylindrical wall surface of the plasma producer 5. Thelower portion of the cylindrical isolating body 2 continues axiallybeyond the end of rod electrode 1 into a cylindrical space defined bythe inner wall surface of plasma producer 5. Therefore it will be seenthat the path of the gas introduced through coupling 6 is first throughthe annular channel 4, then through two axially succeeding tubularpassages 8 and 9, respectively formed by the inner wall surface of thelower portion of the isolating cylindrical body 2 and the innercylindrical wall surface of plasma producer 5. The cone-shaped arc 7 hasan azimuthal magnetic field on the inside and outside thereof, and asthe gas goes through the arc it is partially ionized and the oppositecharge carriers are radially separated by the azimuthal magnetic field.By virtue of the separation, there is less tendency for the oppositecharge carriers to recombine, and consequently there is a higherspecific ionic density when the gas is introduced between the electrodesof the high efficiency plasma producer.

In many instances, it is desired to use a material which emits electronsin the manufacture of the electrodes. On account of the relatively highheat exposure of the isolating body, it should preferably consist of ahigh heat resistant materials.

The method according to the present invention makes possible the safeignition of gas discharges in plasma producers of large dimensions, witheasy manipulation thereof and the guarantee of uniform conditions andfunctioning of the apparatus.

Iclaim:

l. A method of igniting a high efficiency plasma producer withrelatively low voltage comprising the steps of passing a stream ofionizable gas through an ignition aid, said gas following a path definedby a rod electrode and a surrounding isolating body of said aid;producing an electric arc discharge between the end portion of said rodelectrode and a counterelectrode radially spaced and axially beyond saidrod electrode; the electric lines of force of said are being inclined inthe form of a cone with the apex thereof pointing upstream the directionof flow of said ionizable gas in at least that area of said are throughwhich said gas passes thereby producing an azimuthal magnetic field,whereby said gas passing through said inclined arc is at least partiallyionized; radially separating, by virtue of said azimuthal magneticfield, the opposite charge carriers in said partially ionized gas tominimize recombination of said carriers and thereby create a highspecific ionic density in said gas; and then introducing said highspecific ionic density gas into the area between the electrodes of thehigh efficiency plasma producer.

2 A method as claimed in claim 1 wherein backfiring of said arc isprevented by extending said isolating body axially beyond said endportion of the rod electrode to form a first tubular passage and furtherproviding a second and radially larger tubular passage, coaxial with thefirst, and formed by said high efficiency plasma producer acting as saidcounterelectrode, immediately in the direction of gas flow beyond saidfirst tubular passage, so said gas flows along said path andsuccessively through said two tubular passages.

3. A high efficiency plasma producer ignition aid utilizing relativelylow voltage comprising an isolating body having an inner cylindricalwall in which a rod electrode is concentrically mounted and radiallyspaced to form an annular passage, said cylindrical wall extendingaxially beyond one end of said rod electrode forming a first tubularpassage;.a second cylindrical wall coaxial and of larger diameter thanthe first forming a second tubular passage immediately succeeding saidfirst tubular passage; means for feeding ionizable gas to the end ofsaid annular passage opposite said one end of said rod electrode; means.for applying electric potentials having opposite signs respectively tosaid rod electrode and said second cylindrical wall to form an archaving electric lines of force inclined in the form of a cone with theapex thereof pointing upstream the direction of flow of said ionizablegas in at least that area of said are through which said gas passes sothat said gas passing through said inclined arc is partially ionized andthe opposite charge carriers are radially separated by an azimuthalmagnetic field to form a high specific ionic density in said gas, whichhigh specific ionic density gas is then introduced to the electrodes ofthe high efficiency plasma producer.

4. An ignition aid as claimed in claim 3 wherein at least one of theelectrodes consists of electron emitting material.

5. An ignition aid as claimed in claim 3 wherein said first cylindricalwall is made of heat resistant material.

6. An ignition aid as claimed in claim 3 further comprising a securingdevice about said isolating body to secure said ignition aid to saidhigh efficiency plasma producer.

7. An ignition aid as claimed in claim 3 wherein said second cylindricalwall is part of the high efficiency plasma producer.

1. A method of igniting a high efficiency plasma producer withrelatively low voltage comprising the steps of passing a stream ofionizable gas through an ignition aid, said gas following a path definedby a rod electrode and a surrounding isolating body of said aid;producing an electric arc discharge between the end portion of said rodelectrode and a counterelectrode radially spaced and axially beyond saidrod electrode; the electric lines of force of said arc being inclined inthe form of a cone with the apex thereof pointing upstream the directionof flow of said ionizable gas in at least that area of said arc throughwhich said gas passes thereby producing an azimuthal magnetic field,whereby said gas passing through said inclined arc is at least partiallyionized; radially separating, by virtue of said azimuthal magneticfield, the opposite charge carriers in said partially ionized gas tominimize recombination of said carriers and thereby create a highspecific ionic density in said gas; and then introducing said highspecific ionic density gas into the area between the electrodes of thehigh efficiency plasma producer.
 2. A method as claimed in claim 1wherein backfiring of said arc is prevented by extending said isolatingbody axially beyond said end portion of the rod electrode to form afirst tubular passage and further providing a second and radially largertubular passage, coaxial with the first, and formed by said highefficiency plasma producer acting as said counterelectrode, immediatelyin the direction of gas flow beyond said first tubular passage, so saidgas flows along said path and successively through said two tubularpassages.
 3. A high efficiency plasma producer ignition aid utilizingrelatively low voltage comprising an isolating body having an innercylindrical wall in which a rod electrode is concentrically mounted andradially spaced to form an annular passage, said cylindrical wallextending axially beyond one end of said rod electrode forming a firsttubular passage; a second cylindrical wall coaxial and of largerdiameter than the first forming a second tubular passage immediatelysucceeding said first tubular passage; means for feeding ionizable gasto the end of said annular passage opposite said one end of said rodelectrode; means for applying electric potentials having opposite signsrespectively to said rod electrode and said second cylindrical wall toform an arc having electric lines of force inclined in the form of acone with the apex thereof pointing upstream the direction of flow ofsaid ionizable gas in at least that area of said arc through which saidgas passes so that said gas passing through said inclined arc ispartially ionized and the opposite charge carriers are radiallyseparated by an azimuthal magnetic field to form a high specific ionicdensity in said gas, which high specific ionic density gas is thenintroduced to the electrodes of tHe high efficiency plasma producer. 4.An ignition aid as claimed in claim 3 wherein at least one of theelectrodes consists of electron emitting material.
 5. An ignition aid asclaimed in claim 3 wherein said first cylindrical wall is made of heatresistant material.
 6. An ignition aid as claimed in claim 3 furthercomprising a securing device about said isolating body to secure saidignition aid to said high efficiency plasma producer.
 7. An ignition aidas claimed in claim 3 wherein said second cylindrical wall is part ofthe high efficiency plasma producer.